If you just want to prevent them from picking stuff up in your bunker, open the Zone manager (default: SHIFT+Y), [A]dd a new zone, select No NPC Pickup, name it (optionally), select one corner of your bunker, then move the cursor over to select the opposite corner. Press ESC to exit the Zone manager and make sure you save it.
If you don’t want them to pick up anything, talk to them, select b: I want to set some miscellaneous rules. and a: Don't pick up items.…
At world generation, there should have been a Disable NPC Needs mods active by default.
If you removed that mod (or it somehow got overwritten by an other mod you chose), than yes, you need to provide food and water (or other beverages) to your NPC (give it to them to “hold on” or in a trade, they don’t need to be spoonfed) and a chance to sleep.
If you have a faction camp and your NPC(s) are there, they will take the food automatically from the defined stockpile.
There was a bug with NPC and nested containers which prevented them from eating and drinking and I don’t know if it was fixed by now, but I’d assume so.
Unless that changed, yes, randomly generated NPCs are still a thing (given that you didn’t set the Random NPC spawn time to 0) and you may find them on your travels (at “save” locations).
Once they found a place, they stay put and do not move around anymore, according to this post, which - to my knowlege - is still up to date.